Performs the so called "mod 10" algorithm to check the validity of credit card numbers
such as VISA.
In addition to this, the credit card number can be further validated by its length
and prefix, but those properties are depended on the credit card type and such validation
is not performed by this validation rule.
version: $Id: Mod10ValidationRule.java 433543 2006-08-22 06:22:54Z crossley $